The invention relates to impact apparatus in the form of pile-driving apparatus or ram-boring apparatus and to a process for controlling such apparatus.
A device for controlling the forward and reverse strokes of self-driven, pneumatic pile-driving apparatus is described in DE 3104547--JENNE. Such pile-driving apparatus has a tubular housing in which an axially movable ram is located between two stops; the compressed air for the forward and reverse strokes of the ram can be supplied via a control sleeve connected to the compressed air line. This control sleeve is located so that its first, air inlet end, can rotate in a bearing bush disposed near the end of the housing, but cannot move axially. At its other, forward end it has a control head in the form of a piston, which is inserted in a cylindrical bore at the rear end of the ram. The ram itself extends axially in the housing and cannot rotate, and it has at least one pair of radial control ports of different sizes which cooperate with the control sleeve. The control sleeve has respective pairs of control edges associated with said control ports for the forward and reverse strokes of the ram. The edges of each pair are arranged staggered axially with respect to each other, and the pairs of edges are arranged staggered circumferentially to each other.
Despite the relative increase in impact energy obtained by the arrangement of the pair of control ports of different sizes, it is disadvantageous that they act both during the forward stroke and during the reverse stroke. This causes the forward motion of the ram to be impeded.
Moreover the fixed association of pairs of control edges with supplementary ports is a disadvantage, since it both restricts the choice of manufacturing method and complicates the manufacturing process.
This known arrangement of the main and supplementary control ports also results in a poor utilisation of compressed air and compressed air energy, which means that larger compressors and larger on-site installations are necessary. These also have to be transported to and from the site each time, and therefore lead to even greater costs.